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It is conventional in wind energy assessment projects to calculate the expected value of the annual energy production (AEP). However, ignoring the effect of wind speed distribution on the distribution of the annual energy production may cause wrong predictions in the cost analysis. For a better estimation of the payback period, it is essential to accurately determine the confidence levels of the electricity cost around the expected value. Wind speed distributions are commonly represented by the Weibull model. Improved functions or nonparametric functions are preferred in the case of multimodal wind speed distributions. As nonparametric probability density function, the optimum spline based functions are implemented and compared to Weibull, Weibull & Weibull for two different wind sites. The results show that the spline based probability density functions produce minimum fitting error for the analyzed cases. Once the wind speed distributions are characterized, random wind speeds are generated to calculate the AEP distributions by Monte Carlo simulations. The cost analysis is then carried out based on the AEP distributions which includes the determination of the confidence levels. It is observed that the confidence levels of the electricity costs which are not falling close to the expected cost region are much greater.
Munir Ali Elfarra; Mustafa Kaya. Estimation of electricity cost of wind energy using Monte Carlo simulations based on nonparametric and parametric probability density functions. Alexandria Engineering Journal 2021, 60, 3631 -3640.
AMA StyleMunir Ali Elfarra, Mustafa Kaya. Estimation of electricity cost of wind energy using Monte Carlo simulations based on nonparametric and parametric probability density functions. Alexandria Engineering Journal. 2021; 60 (4):3631-3640.
Chicago/Turabian StyleMunir Ali Elfarra; Mustafa Kaya. 2021. "Estimation of electricity cost of wind energy using Monte Carlo simulations based on nonparametric and parametric probability density functions." Alexandria Engineering Journal 60, no. 4: 3631-3640.
Ultra-high-strength concrete is a newly developed construction material that has a minimum 120 MPa or higher compressive strength. Recently, the usage of high-strength and ultra-high-strength concretes has become widespread due to the enhancement of the concrete technology. Many civil engineering structures constructed by using concrete materials are usually subjected to, in addition to static loads, dynamic loads due to earthquakes, wind and storm, impact and blast, which take place under high energy and high strain rate values. The effects of such loadings on the structure must be understood thoroughly. In recent years, the withstanding of a structure on these loading conditions has become a crucial issue for its impact on the economy and human safety. One of the approaches to fulfill these requirements is to develop high-strength or ultra high-strength concretes (UHSCs). In this study, an ultra-high-strength concrete with a compressive strength of 135 MPa was designed and developed. In order to determine the dynamic behavior of this UHSC, the specimens at three height/diameter ratios (approximately, 0.6, 1.0 and 1.2) were extracted from the prepared concrete mixtures. These concrete specimens were tested to determine both the quasi-static and dynamic compressive behaviors of the developed concrete. In the quasi-static compression tests, cylindrical specimens and a conventional compressive testing machine were used. In order to study the dynamic compressive behavior, a Split Hopkinson Pressure Bar (SHPB) test setup was used. In this test system, the time variations of compressive strength, the strain and strain rates under uniaxial pressure loading were experimentally evaluated and the deformation and fracturing processes of the specimens were recorded using a high-speed camera. The test results, based on the testing of 21 different specimens, have shown that the dynamic compressive strength values of the developed concrete varied in the range of 143 to 253 MPa, while the strain rate values varied in the range of 353 s−1 to 1288 s−1. Using the data generated in the SHPB tests, the parameters present in a Johnson–Holmquist–Cook concrete material model, which is used in numerical studies on the high strain rate behavior of concretes, were evaluated.
Ahmet Reha Gunay; Sami Karadeniz; Mustafa Kaya. An Experimental Study on the Dynamic Behavior of an Ultra High-Strength Concrete. Applied Sciences 2020, 10, 1 .
AMA StyleAhmet Reha Gunay, Sami Karadeniz, Mustafa Kaya. An Experimental Study on the Dynamic Behavior of an Ultra High-Strength Concrete. Applied Sciences. 2020; 10 (12):1.
Chicago/Turabian StyleAhmet Reha Gunay; Sami Karadeniz; Mustafa Kaya. 2020. "An Experimental Study on the Dynamic Behavior of an Ultra High-Strength Concrete." Applied Sciences 10, no. 12: 1.
Computational fluid dynamics (CFD) is a powerful tool to estimate accurately the aerodynamic loads on wind turbine blades at the expense of high requirements like the duration of computation. Such requirements grow in the case of blade shape optimization in which several analyses are needed. A fast and reliable way to mimic the CFD solutions is to use surrogate models. In this study, a machine learning technique, the support vector regression (SVR) method based on a set of CFD solutions, is used as the surrogate model. CFD solutions are calculated by solving the Reynolds-averaged Navier–Stokes equation with the k-epsilon turbulence model using a commercial solver. The support vector regression model is then trained to give a functional relationship between the spanwise twist distribution and the generated torque. The smooth twist distribution is defined using a three-node cubic spline with four parameters in total. The optimum twist is determined for two baseline blade cases: the National Renewable Energy Laboratory (NREL) Phase II and Phase VI rotor blades. In the optimization process, extremum points that give the maximum torque are easily determined since the SVR gives an analytical model. Results show that it is possible to increase the torque generated by the NREL VI blade more than 10% just by redistributing the spanwise twist without carrying out a full geometry optimization of the blade shape with many shape-defining parameters. The increase in torque for the NREL II case is much higher.
Mustafa Kaya. A CFD Based Application of Support Vector Regression to Determine the Optimum Smooth Twist for Wind Turbine Blades. Sustainability 2019, 11, 4502 .
AMA StyleMustafa Kaya. A CFD Based Application of Support Vector Regression to Determine the Optimum Smooth Twist for Wind Turbine Blades. Sustainability. 2019; 11 (16):4502.
Chicago/Turabian StyleMustafa Kaya. 2019. "A CFD Based Application of Support Vector Regression to Determine the Optimum Smooth Twist for Wind Turbine Blades." Sustainability 11, no. 16: 4502.
Mustafa Kaya; Munir Elfarra; Ferhat Kadioglu. Investigation of the Effect of Taper Stacking Location on Drag Force for ONERA M6 Wing. AIAA Scitech 2019 Forum 2019, 1 .
AMA StyleMustafa Kaya, Munir Elfarra, Ferhat Kadioglu. Investigation of the Effect of Taper Stacking Location on Drag Force for ONERA M6 Wing. AIAA Scitech 2019 Forum. 2019; ():1.
Chicago/Turabian StyleMustafa Kaya; Munir Elfarra; Ferhat Kadioglu. 2019. "Investigation of the Effect of Taper Stacking Location on Drag Force for ONERA M6 Wing." AIAA Scitech 2019 Forum , no. : 1.
The common approach to wind energy feasibility studies is to use Weibull distribution for wind speed data to estimate the annual energy production (AEP). However, if the wind speed data has more than one mode in the probability density, the conventional distributions including Weibull fail to fit the wind speed data. This highly affects the technical and economic assessment of a wind energy project by causing crucial errors. This paper presents a novel way to define the probability density for wind speed data using splines. The splines are determined as a solution of constrained optimization problems. The constraints are the characteristics of probability density functions. The proposed method is implemented for different wind speed distributions including multimodal data and compared with Weibull, Weibull and Weibull and Beta Exponentiated Power Lindley (BEPL) distributions. It is also compared with two other nonparametric distributions. The results show that the spline-based probability density functions produce a minimum fitting error for all the analyzed cases. The AEP calculated based on this method is considered to have high fidelity, which will decrease the investment risk.
Munir Ali Elfarra; Mustafa Kaya. Comparison of Optimum Spline-Based Probability Density Functions to Parametric Distributions for the Wind Speed Data in Terms of Annual Energy Production. Energies 2018, 11, 3190 .
AMA StyleMunir Ali Elfarra, Mustafa Kaya. Comparison of Optimum Spline-Based Probability Density Functions to Parametric Distributions for the Wind Speed Data in Terms of Annual Energy Production. Energies. 2018; 11 (11):3190.
Chicago/Turabian StyleMunir Ali Elfarra; Mustafa Kaya. 2018. "Comparison of Optimum Spline-Based Probability Density Functions to Parametric Distributions for the Wind Speed Data in Terms of Annual Energy Production." Energies 11, no. 11: 3190.
The stacking axis locations for twist and taper distributions along the span of a wind turbine blade are optimized to maximize the rotor torque and/or to minimize the thrust. A neural networks (NN)-based model is trained for the torque and thrust values calculated using a computational fluid dynamics (CFD) solver. Once the model is obtained, constrained and unconstrained optimization is conducted. The constraints are the torque or the thrust values of the baseline turbine blade. The baseline blade is selected as the wind turbine blade used in the National Renewable Energy Laboratory (NREL) Phase VI rotor model. The Reynolds averaged Navier–Stokes (RANS) computations are done using the FINE/turbo flow solver developed by NUMECA International. The k-epsilon turbulence model is used to calculate the eddy viscosity. It is observed that achieving the same torque value as the baseline value is possible with about 5% less thrust. Similarly, the torque is increased by about 4.5% while maintaining the baseline thrust value.
Mustafa Kaya; Munir Elfarra. Optimization of the Taper/Twist Stacking Axis Location of NREL VI Wind Turbine Rotor Blade Using Neural Networks Based on Computational Fluid Dynamics Analyses. Journal of Solar Energy Engineering 2018, 141, 1 .
AMA StyleMustafa Kaya, Munir Elfarra. Optimization of the Taper/Twist Stacking Axis Location of NREL VI Wind Turbine Rotor Blade Using Neural Networks Based on Computational Fluid Dynamics Analyses. Journal of Solar Energy Engineering. 2018; 141 (1):1.
Chicago/Turabian StyleMustafa Kaya; Munir Elfarra. 2018. "Optimization of the Taper/Twist Stacking Axis Location of NREL VI Wind Turbine Rotor Blade Using Neural Networks Based on Computational Fluid Dynamics Analyses." Journal of Solar Energy Engineering 141, no. 1: 1.
Munir Elfarra; Mustafa Kaya; Ferhat Kadioglu. A Parametric CFD Study for the Effect of Spanwise Parabolic Chord Distribution on the Thrust of an Untwisted Helicopter Rotor Blade. 2018 AIAA Aerospace Sciences Meeting 2018, 1 .
AMA StyleMunir Elfarra, Mustafa Kaya, Ferhat Kadioglu. A Parametric CFD Study for the Effect of Spanwise Parabolic Chord Distribution on the Thrust of an Untwisted Helicopter Rotor Blade. 2018 AIAA Aerospace Sciences Meeting. 2018; ():1.
Chicago/Turabian StyleMunir Elfarra; Mustafa Kaya; Ferhat Kadioglu. 2018. "A Parametric CFD Study for the Effect of Spanwise Parabolic Chord Distribution on the Thrust of an Untwisted Helicopter Rotor Blade." 2018 AIAA Aerospace Sciences Meeting , no. : 1.
Mustafa Kaya; Munir Elfarra; Ferhat Kadioglu. A Parametric CFD Study for the Effect of Taper/Twist Stacking Point Location on the Torque of NREL VI Wind Turbine Rotor Blade. 2018 Wind Energy Symposium 2018, 1 .
AMA StyleMustafa Kaya, Munir Elfarra, Ferhat Kadioglu. A Parametric CFD Study for the Effect of Taper/Twist Stacking Point Location on the Torque of NREL VI Wind Turbine Rotor Blade. 2018 Wind Energy Symposium. 2018; ():1.
Chicago/Turabian StyleMustafa Kaya; Munir Elfarra; Ferhat Kadioglu. 2018. "A Parametric CFD Study for the Effect of Taper/Twist Stacking Point Location on the Torque of NREL VI Wind Turbine Rotor Blade." 2018 Wind Energy Symposium , no. : 1.
Hüseyin Emrah Konokman; Altan Kayran; Mustafa Kaya. Aircraft vulnerability assessment against fragmentation warhead. Aerospace Science and Technology 2017, 67, 215 -227.
AMA StyleHüseyin Emrah Konokman, Altan Kayran, Mustafa Kaya. Aircraft vulnerability assessment against fragmentation warhead. Aerospace Science and Technology. 2017; 67 ():215-227.
Chicago/Turabian StyleHüseyin Emrah Konokman; Altan Kayran; Mustafa Kaya. 2017. "Aircraft vulnerability assessment against fragmentation warhead." Aerospace Science and Technology 67, no. : 215-227.
The path of dual airfoils in a biplane configuration undergoing a combined, non–sinusoidal pitching and plunging motion is optimized for maximum thrust and/or propulsive efficiency. The non–sinusoidal, periodic flapping motion is described using Non-Uniform Rational B-Splines (NURBS). The Response Surface Methodology (RSM) is employed for the optimization of NURBS parameters in a parallel computing environment. A gradient based optimization algorithm, steepest ascent method is started from the optimum point of response surfaces. Unsteady, low speed laminar flows are also computed in parallel using a Navier-Stokes solver based on domain decomposition. It is shown that the parallel optimization process with RSM suggests a quick and accurate initial guess for a gradient based optimization algorithm.
Mustafa Kaya; Ismail H. Tuncer. Path Optimization of Dual Airfoils Flapping in a Biplane Configuration with RSM in a Parallel Computing Environment. Lecture Notes in Computational Science and Engineering 2010, 74, 83 -90.
AMA StyleMustafa Kaya, Ismail H. Tuncer. Path Optimization of Dual Airfoils Flapping in a Biplane Configuration with RSM in a Parallel Computing Environment. Lecture Notes in Computational Science and Engineering. 2010; 74 ():83-90.
Chicago/Turabian StyleMustafa Kaya; Ismail H. Tuncer. 2010. "Path Optimization of Dual Airfoils Flapping in a Biplane Configuration with RSM in a Parallel Computing Environment." Lecture Notes in Computational Science and Engineering 74, no. : 83-90.
Mustafa Kaya; Ismail H. Tuncer; Kevin D. Jones; Max F. Platzer. Optimization of Flapping Motion Parameters for Two Airfoils in a Biplane Configuration. Journal of Aircraft 2009, 46, 583 -592.
AMA StyleMustafa Kaya, Ismail H. Tuncer, Kevin D. Jones, Max F. Platzer. Optimization of Flapping Motion Parameters for Two Airfoils in a Biplane Configuration. Journal of Aircraft. 2009; 46 (2):583-592.
Chicago/Turabian StyleMustafa Kaya; Ismail H. Tuncer; Kevin D. Jones; Max F. Platzer. 2009. "Optimization of Flapping Motion Parameters for Two Airfoils in a Biplane Configuration." Journal of Aircraft 46, no. 2: 583-592.
The path of dual airfoils in a biplane configuration undergoing a combined, non-sinusoidal pitching and plunging motion is optimized for maximum thrust and/or propulsive efficiency. The non-sinusoidal, periodic flapping motion is described using Non-Uniform Rational B-Splines (NURBS). A gradient based algorithm is then employed for the optimization of the NURBS parameters. Unsteady, low speed laminar flows are computed using a Navier-Stokes solver in a parallel computing environment based on domain decomposition. The numerical evaluation of the gradient vector components, which requires unsteady flow solutions, is also performed in parallel. It is shown that the thrust generation may significantly be increased in comparison to the sinusoidal flapping motion.
Mustafa Kaya; I. H Tuncer. Non-Sinusoidal Path Optimization of Dual Airfoils Flapping in a Biplane Configuration. Lecture Notes in Computational Science and Engineering 2008, 59 -66.
AMA StyleMustafa Kaya, I. H Tuncer. Non-Sinusoidal Path Optimization of Dual Airfoils Flapping in a Biplane Configuration. Lecture Notes in Computational Science and Engineering. 2008; ():59-66.
Chicago/Turabian StyleMustafa Kaya; I. H Tuncer. 2008. "Non-Sinusoidal Path Optimization of Dual Airfoils Flapping in a Biplane Configuration." Lecture Notes in Computational Science and Engineering , no. : 59-66.
Mustafa Kaya; Ismail H. Tuncer. Nonsinusoidal Path Optimization of a Flapping Airfoil. AIAA Journal 2007, 45, 2075 -2082.
AMA StyleMustafa Kaya, Ismail H. Tuncer. Nonsinusoidal Path Optimization of a Flapping Airfoil. AIAA Journal. 2007; 45 (8):2075-2082.
Chicago/Turabian StyleMustafa Kaya; Ismail H. Tuncer. 2007. "Nonsinusoidal Path Optimization of a Flapping Airfoil." AIAA Journal 45, no. 8: 2075-2082.
Mustafa Kaya; Ismail H. Tuncer; Kevin Jones; Max Platzer. Optimization of Aeroelastic Flapping Motion of Thin Airfoils in a Biplane Configuration for Maximum Thrust. 37th AIAA Fluid Dynamics Conference and Exhibit 2007, 1 .
AMA StyleMustafa Kaya, Ismail H. Tuncer, Kevin Jones, Max Platzer. Optimization of Aeroelastic Flapping Motion of Thin Airfoils in a Biplane Configuration for Maximum Thrust. 37th AIAA Fluid Dynamics Conference and Exhibit. 2007; ():1.
Chicago/Turabian StyleMustafa Kaya; Ismail H. Tuncer; Kevin Jones; Max Platzer. 2007. "Optimization of Aeroelastic Flapping Motion of Thin Airfoils in a Biplane Configuration for Maximum Thrust." 37th AIAA Fluid Dynamics Conference and Exhibit , no. : 1.
Mustafa Kaya; Ismail H. Tuncer; Kevin Jones; Max Platzer. Optimization of Flapping Motion of Airfoils in Biplane Configuration for Maximum Thrust and/or Efficiency. 45th AIAA Aerospace Sciences Meeting and Exhibit 2007, 1 .
AMA StyleMustafa Kaya, Ismail H. Tuncer, Kevin Jones, Max Platzer. Optimization of Flapping Motion of Airfoils in Biplane Configuration for Maximum Thrust and/or Efficiency. 45th AIAA Aerospace Sciences Meeting and Exhibit. 2007; ():1.
Chicago/Turabian StyleMustafa Kaya; Ismail H. Tuncer; Kevin Jones; Max Platzer. 2007. "Optimization of Flapping Motion of Airfoils in Biplane Configuration for Maximum Thrust and/or Efficiency." 45th AIAA Aerospace Sciences Meeting and Exhibit , no. : 1.
Mustafa Kaya; Ismail H. Tuncer. Path Optimization of Flapping Airfoils Based on NURBS. Parallel Computational Fluid Dynamics 2006 2007, 285 -292.
AMA StyleMustafa Kaya, Ismail H. Tuncer. Path Optimization of Flapping Airfoils Based on NURBS. Parallel Computational Fluid Dynamics 2006. 2007; ():285-292.
Chicago/Turabian StyleMustafa Kaya; Ismail H. Tuncer. 2007. "Path Optimization of Flapping Airfoils Based on NURBS." Parallel Computational Fluid Dynamics 2006 , no. : 285-292.
John Young; J. C. S. Lai; M. Kaya; I. H. Tuncer. Thrust and Efficiency of Propulsion by Oscillating Foils. Computational Fluid Dynamics 2004 2006, 313 -318.
AMA StyleJohn Young, J. C. S. Lai, M. Kaya, I. H. Tuncer. Thrust and Efficiency of Propulsion by Oscillating Foils. Computational Fluid Dynamics 2004. 2006; ():313-318.
Chicago/Turabian StyleJohn Young; J. C. S. Lai; M. Kaya; I. H. Tuncer. 2006. "Thrust and Efficiency of Propulsion by Oscillating Foils." Computational Fluid Dynamics 2004 , no. : 313-318.
Ismail H. Tuncer; Mustafa Kaya. Optimization of Flapping Airfoils For Maximum Thrust and Propulsive Efficiency. AIAA Journal 2005, 43, 2329 -2336.
AMA StyleIsmail H. Tuncer, Mustafa Kaya. Optimization of Flapping Airfoils For Maximum Thrust and Propulsive Efficiency. AIAA Journal. 2005; 43 (11):2329-2336.
Chicago/Turabian StyleIsmail H. Tuncer; Mustafa Kaya. 2005. "Optimization of Flapping Airfoils For Maximum Thrust and Propulsive Efficiency." AIAA Journal 43, no. 11: 2329-2336.
Ismail H. Tuncer; Mustafa Kaya. Thrust Generation Caused by Flapping Airfoils in a Biplane Configuration. Journal of Aircraft 2003, 40, 509 -515.
AMA StyleIsmail H. Tuncer, Mustafa Kaya. Thrust Generation Caused by Flapping Airfoils in a Biplane Configuration. Journal of Aircraft. 2003; 40 (3):509-515.
Chicago/Turabian StyleIsmail H. Tuncer; Mustafa Kaya. 2003. "Thrust Generation Caused by Flapping Airfoils in a Biplane Configuration." Journal of Aircraft 40, no. 3: 509-515.
Ismail H. Tuncer; Mustafa Kaya. Parallel Computation of Flows Around Flapping Airfoils in Biplane Configuration. Parallel Computational Fluid Dynamics 2002 2003, 523 -530.
AMA StyleIsmail H. Tuncer, Mustafa Kaya. Parallel Computation of Flows Around Flapping Airfoils in Biplane Configuration. Parallel Computational Fluid Dynamics 2002. 2003; ():523-530.
Chicago/Turabian StyleIsmail H. Tuncer; Mustafa Kaya. 2003. "Parallel Computation of Flows Around Flapping Airfoils in Biplane Configuration." Parallel Computational Fluid Dynamics 2002 , no. : 523-530.